Rheology is the study of flow and deformation of materials. It is important to control the external factors that affect a material while it is being rheologically tested, in order to correctly attribute resulting phenomena. External factors that may need to be controlled include, but aren't limited to, temperature, light sources, and energy fields.
It is important to control temperature accurately, whether it is to be provided isothermally or in a ramp. Some materials show changes in modulus (stiffness) as large as 20%/1° C. And some rheological phenomena are also attributable to external influences such as, but not exclusively, various wavelengths of light, external energy fields and pressure. Not all of these can be or are required to be controlled at once, which can result in the use of multiple types of environmental controller based on the requirements of a sample under test.
But changing between different environmental controllers tends to be quite difficult in current rheometer instrumentation. Typically, users must mechanically align top and bottom parts, and then set up a series of electrical and fluid connections.